Before meeting the artist Mr Jason Brooks at his handsome, double-height studio overlooking Cadogan Square in Knightsbridge, I diligently note down the titles of the work in his new London show, Ultraflesh. I've tried, but I can't quite make a link between the names and the paintings: why, for example, is a bunch of flowers haphazardly tossed in a bowl called "A Taste of Sugar"? And what to make of "Dreams of Misty" and "Dark Submission"?

The 44-year-old Mr Brooks can't quite suppress a smile. "I like my titles to have no relationship to the subject at all," he explains. "So all these works are titled after 1970s-onwards porn movies. They have the greatest titles you could ever wish to imagine: I've got reams - reams! - of them and some are actually quite witty and beautiful. But, placed in another context, they mean something completely different, which is incredibly refreshing."

"What's that one called?" I ask, gesturing towards a depiction of Jesus Christ that rests on an easel. "That's 'Tangerine' - God knows what kind of porn movie that is," says Mr Brooks. "As an artist, you spend a lot of time by yourself, so you've got to motivate yourself in a way. There's a serious side, but you've also got to be slightly playful to keep yourself doing this activity." He pauses, "I realise that sounds really sad, some guy sitting at his computer looking at porn movie titles: 'I've found another great one!'"

Where Mr Brooks is concerned, things are rarely what they seem. Since the early 1990s, when he graduated with a master's degree in fine art from Chelsea College of Art and Design, he has been one of Britain's foremost photorealist painters. His immaculate, disconcertingly vivid portraits are particularly prized; sitters have included a tattoo artist, the racing driver Mr Jenson Button, a Nobel prize-winning scientist and supermodels Mses Claudia Schiffer and Natalia Vodianova. His methods have changed little over the years: he photographs his subject - formerly with a plate camera, now digitally - and then painstakingly recreates the image using an airbrush and acrylic paint. The process can take months.

Mr Brooks relishes messing around with viewers' perceptions. Across a gallery, his paintings might appear to be slick photographic images, but up close the canvases can be surprisingly rough, with white marks literally scratched into the black pigment. In his newer works, what look like textured, impasto surfaces turn out to be completely flat. Other times the shock is a more visceral one: in 2003, Mr Brooks produced a series of vast canvases set in the English countryside. A model's sculpted legs fill the foreground and they have the gloss of fashion advertising; it takes a couple of moments to realise that the woman is enjoying an alfresco pee.

Mr Brooks' choice of a fine airbrush to create detail in his paintings is a very deliberate one. "We're used to everything being airbrushed out, whereas obviously I'm keen to airbrush everything in," he says, glancing over at his portrait of Ms Vodianova. "Not that there's much to airbrush out with Natalia, but I feel one of my missions in life is to put all those things back in, because those nuances and hang-ups are often the things you fall in love with. They make a person individual, so for me those are the things we should champion. Imperfection, but they are not imperfections."

the work

"Milk Maid", 2012 - 13

Jason Brooks
Courtesy of Marlborough Contemporary and the artist

"Natalia (1-4)", 2012

Jason Brooks
Courtesy of Marlborough Contemporary and the artist

"Tangerine", 2012

Jason Brooks
Courtesy of Marlborough Contemporary and the artist

"Squealer", 2011 - 13

Jason Brooks
Courtesy of Marlborough Contemporary and the artist

"Control 8", 2012 - 13

Jason Brooks
Courtesy of Marlborough Contemporary and the artist

"A Taste of Sugar", 2010

Jason Brooks
Courtesy of Marlborough Contemporary and the artist

"Sweet Alice", 2013

Jason Brooks
Courtesy of Marlborough Contemporary and the artist

"Blow Bang 7", 2012 - 13

Jason Brooks
Courtesy of Marlborough Contemporary and the artist

"Wad So FJohnny", 2012 - 13

Ultraflesh is a departure for Mr Brooks, in part because there are no portraits in the show. The inspiration for his new paintings is found art that he has photographed, cropped, manipulated and meticulously reproduced - coffee stains, wonky signatures and all. He picked up much of the work in car-boot sales and teashops in Kent; the most he paid was £150, while two of the new works were based on a batch of six paintings that cost £4.

Perhaps the most bizarre object he bought was a small iron sculpture that appears to show a man in Russian costume riding a sheep backwards lifting its hind-quarters over a bucket. "I found it on a market stall," Mr Brooks remembers. "The guy selling it looked really shocked when I picked it up and said, 'If you don't mind me asking, why are you buying it?' So I replied, 'Why are you selling it?' And he said, 'Yes, it is rather odd.'" Mr Brooks has blown up this curio to almost life-size and turned it into a cheeky self-portrait, one of two sculptures in the show.

When asked if there is one theme that unites all the found art he used as the basis for Ultraflesh, Mr Brooks goes silent for a few seconds. "It's love," he says eventually. "Every work of art I chose is made with love. The essence of an amateur painter - and I'm not saying that in a demeaning way - is their struggle to articulate something. You can see it, it becomes charged: someone has really worked to pull this thing out from nothing to create something."